From b238c756da5b8c54437e58c2878ecae7467079eb Mon Sep 17 00:00:00 2001 From: =?utf8?q?Jos=C3=A9=20Fonseca?= Date: Fri, 7 Nov 2014 21:20:25 +0000 Subject: [PATCH] util/format: Fix clamping to 32bit integers. Use clamping constants that guarantee no integer overflows. As spotted by Chris Forbes. This causes the code to change as: - value |= (uint32_t)CLAMP(src[0], 0.0f, 4294967295.0f); + value |= (uint32_t)CLAMP(src[0], 0.0f, 4294967040.0f); - value |= (uint32_t)((int32_t)CLAMP(src[0], -2147483648.0f, 2147483647.0f)); + value |= (uint32_t)((int32_t)CLAMP(src[0], -2147483648.0f, 2147483520.0f)); Reviewed-by: Roland Scheidegger --- src/gallium/auxiliary/util/u_format_pack.py | 27 +++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/src/gallium/auxiliary/util/u_format_pack.py b/src/gallium/auxiliary/util/u_format_pack.py index 90f348ea580..d5138cc0577 100644 --- a/src/gallium/auxiliary/util/u_format_pack.py +++ b/src/gallium/auxiliary/util/u_format_pack.py @@ -207,9 +207,36 @@ def get_one_shift(type): assert False +def truncate_mantissa(x, bits): + '''Truncate an integer so it can be represented exactly with a floating + point mantissa''' + + assert isinstance(x, (int, long)) + + s = 1 + if x < 0: + s = -1 + x = -x + + # We can represent integers up to mantissa + 1 bits exactly + mask = (1 << (bits + 1)) - 1 + + # Slide the mask until the MSB matches + shift = 0 + while (x >> shift) & ~mask: + shift += 1 + + x &= mask << shift + x *= s + return x + + def value_to_native(type, value): '''Get the value of unity for this type.''' if type.type == FLOAT: + if type.size <= 32 \ + and isinstance(value, (int, long)): + return truncate_mantissa(value, 23) return value if type.type == FIXED: return int(value * (1 << (type.size/2))) -- 2.30.2